(a) Field of the Invention
The present invention relates to a plasma display device and a method for driving a plasma display panel (PDP), and more particularly, to a frequency of a sustain discharge pulse applied to the PDP.
(b) Description of the Related Art
Plasma display devices are displays that use a PDP for displaying characters or images using plasma generated by gas discharge. The PDP includes, according to its size, more than several tens to millions of pixels (discharge cells) arranged in the form of a matrix.
FIG. 1 is a perspective view illustrating part of a general PDP. Scan electrodes 4 and sustain electrodes 5 covered with a dielectric layer 2 and a protective layer 3 are arranged in pairs in parallel on a first glass substrate 1. A plurality of address electrodes 8 covered with an insulation layer 7 are arranged on a second glass substrate 6. Barrier ribs 9 are formed in parallel with the address electrodes 8 on the insulation layer 7 such that each barrier rib 9 is interposed between the adjacent address electrodes 8. A phosphor 10 is coated on the surface of the insulation layer 7 and on both sides of each partition wall 9. The first and second glass substrates 1 and 6 are arranged to face each other while defining a discharge space 11 therebetween so that the address electrodes 8 are orthogonal to the scan electrodes 4 and sustain electrodes 5. In the discharge space, a discharge cell 12 is formed at an intersection between each address electrode 8 and each pair of the scan electrodes 4 and sustain electrodes 5.
In general, a process for driving the AC PDP can be expressed by temporal operational periods, i.e., a reset period, an address period and a sustain period. The reset period is a period wherein the state of each cell is intialized such that an addressing operation of each cell is smoothly performed. The address period is a period wherein an address voltage is applied to an addressed cell to accumulate wall charges on the addressed cell in order to select a cell to be turned on and a cell not to be turned on in the PDP. During the sustain period, a sustain discharge pulse is alternately applied to the scan electrode 4 and the sustain electrode 5 in pairs. A difference in voltage between the scan electrode 4 and the sustain electrode 5 alternates between sustain discharge voltages Vs and −Vs. In this case, when a wall voltage is applied between the scan electrode Y and the sustain electrode X by address discharge during the address period, sustain discharge is created in the scan electrode Y and the sustain electrode X by the wall voltage and the sustain discharge voltage Vs.
Discharge efficiency is changed by the frequency of the sustain discharge pulse during the sustain period. A known technique related to the frequency of the sustain discharge pulse is disclosed in U.S. Pat. No. 6,356,017 issued to Makino where it is suggested that the discharge efficiency can be improved by having the frequency f of the sustain discharge pulse satisfy the relationship of the following Equation 1:
  f  ≥                    μ        i            ⁢      Vs              π      ⁢                          ⁢              d        2                            where, μi is ion mobility, Vs is a sustain voltage, d is a gap between the scan electrode and the sustain electrode.        
Recently, also for the purpose of improving the discharge efficiency, a partial pressure of xenon (Xe) gas injected as a discharge gas into the discharge space has been increased over 10%. In general, when the partial pressure of Xe is low, Xe* monomer emits light. When the partial pressure of Xe is increased over 10%, (Xe—Xe)* dimer emits light. The Xe* monomer emits a 147 nm resonance line. Ultraviolet rays are absorbed in the 147 nm resonance line before this line is absorbed into Xe and arrives at a phosphor. In addition, when Xe* is struck by electrons, it is changed to Xe. As such, the ultraviolet ray can not be converted to a visible ray, which results in energy loss.
(Xe—Xe)* dimer emits a 173 nm molecular beam. This beam arrives at the phosphor directly without being absorbed by Xe or (Xe—Xe), which leads to a good energy efficiency. In addition, since the (Xe—Xe)* dimer delivers energy to the phosphor rapidly, the risk of it being struck by electrons is greatly reduced. Accordingly, the frequency range suggested by Makino is not proper when (Xe—Xe)* dimer is used to improve the energy efficiency. In addition, because the frequency suggested by Makino is very high, the sustain discharge pulse must use a sinusoidal wave instead of a square wave.